The woman said she only learnt overnight that Shayden Thorne, 25, was being tortured in the prison where he has been held for 18 months.

Shayden Thorne, 25, is in custody facing allegations of terrorism.

"According to the documents that I've received from the lawyer, I now know that he has been physically tortured," she told reporters on Thursday.

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"He's been tied, hands and wrists behind his back, he's been punched in his genitals and he's passed out from that.

"His tying up has been for two weeks straight, as well as the sleep deprivation, bright lights and everything.

"It's like Guantanamo."

The woman doubted Foreign Minister Bob Carr's claim the federal government had made 50 representations to Saudi Arabian authorities on Shayden's behalf and sent consular officials to visit him six times over the past 18 months.

"That's a stretch - not possible," she said.

"More like 15, not 50."

She said Saudi authorities had linked her son to funding terrorism activities.

But not only did she not believe he was capable of supporting terrorists, he and his brother Junaid, 23, were both always short of money, like normal men of that age.

Junaid is now in hiding in Saudi Arabia after being arrested and detained for two months for protesting about his brother's imprisonment.

The men's mother said while it had been alleged Shayden had terrorist material on a laptop, the computer had been borrowed from a mosque or a friend to watch movies, and it had not been produced in the three court hearings that had been held so far.

A final hearing is expected late next month or early in June, when Shayden will learn his fate.

Responding to suggestions that Shayden could face the death penalty, she said, "I haven't thought about that yet."

"I guess he's going to be in prison for a long time."

She feared the boys were "disadvantaged" for being Aboriginal and Muslim - ironically in a Muslim country.

"Shame on them," she said of the Saudi government, "that they're treating Muslims like that".

The boys' aunt, Stephanie Riley, said the family was worried the Saudi secret service would make them "disappear".

"We don't know what can happen," Ms Riley said.

Foreign Minister Bob Carr later disputed the claims of torture.

He said there had been more than 50 representations and six visits by embassy officials over 18 months to Mr Thorne, but his mother's claims were the first embassy staff had heard of torture complaints.

"On the contrary, I'm advised by our embassy that Mr Thorne has not informed them of any torture in prison - he's complained about a lack of sunlight, exercise and variations in food," he told Sky News.

"So, that's advice from my embassy. I have to rely on that ... that he has not made complaints to them in the contact they've had with him about torture."

Senator Carr said he understood Mr Thorne's mother's distress.

"I just point out to her very politely, very respectfully, I do not have the capacity to bring them home," he said.